Generally, the widely-used peripheral input device of a computer system includes for example a mouse, a keyboard, a trackball, or the like. Via the keyboard, characters or symbols can be directly inputted into the computer system. As a consequence, most users and most manufacturers of input devices pay attention to the development of keyboards. As known, a keyboard with scissors-type connecting elements is one of the widely-used keyboards.
Hereinafter, a key structure with a scissors-type connecting element of a conventional keyboard will be illustrated with reference to FIGS. 1 and 2. FIG. 1 is a schematic exploded view illustrating a conventional key structure. FIG. 2 is a schematic side cross-sectional view of the conventional key structure. As shown in FIGS. 1 and 2, the conventional key structure 1 comprises a keycap 11, a scissors-type connecting element 12, a rubbery elastomer 13, a membrane switch circuit member 14 and a metallic base plate 15. The keycap 11, the scissors-type connecting element 12 and the rubbery elastomer 13 are supported by the metallic base plate 15. The membrane switch circuit member 14 is disposed under the metallic base plate 15. The scissors-type connecting element 12 is used for connecting the metallic base plate 15 with the keycap 11. Consequently, the keycap 11 is movably fixed on the metallic plate 15. The metallic base plate 15 is made of a metallic material.
The membrane switch circuit member 14 comprises plural key intersections (not shown). When one of the plural key intersections is triggered, a corresponding key signal is generated. Consequently, a computer (not shown) in communication with the keyboard executes a command corresponding to the key signal. The rubbery elastomer 13 is disposed on the membrane switch circuit member 14. Each rubbery elastomer 13 is aligned with a corresponding key intersection. When the rubbery elastomer 13 is depressed, the rubbery elastomer 13 is subjected to deformation to push the corresponding key intersection of the membrane switch circuit member 14. Consequently, the corresponding key signal is generated.
The metallic base plate 15 comprises a base opening 151. The rubbery elastomer 13 is penetrated through the base opening 151 and disposed on the membrane switch circuit member 14. Moreover, the metallic base plate 15 further comprises a movable base hook 152 and a fixed base hook 153. The movable base hook 152 and the fixed base hook 153 are connected with the scissors-type connecting element 12. Similarly, the keycap 11 comprises a movable keycap hook 111 and a fixed keycap hook 112. The movable keycap hook 111 and the fixed keycap hook 112 are connected with the scissors-type connecting element 12.
The scissors-type connecting element 12 is arranged between the metallic base plate 15 and the keycap 11, and the metallic base plate 15 and the keycap 11 are connected with each other through the scissors-type connecting element 12. The scissors-type connecting element 12 comprises a first frame 121 and a second frame 122. A first end of the first frame 121 is connected with the keycap 11. A second end of the first frame 121 is connected with the metallic base plate 15. The rubbery elastomer 13 is enclosed by the scissors-type connecting element 12, and arranged between the keycap 11 and the membrane switch circuit member 14. Moreover, the first frame 121 comprises a first keycap post 1211 and a first base post 1212. The first frame 121 is connected with the movable keycap hook 111 of the keycap 11 through the first keycap post 1211. The first frame 121 is connected with the fixed base hook 153 of the metallic base plate 15 through the first base post 1212. The second frame 122 is combined with the first frame 121. A first end of the second frame 122 is connected with the metallic base plate 15. A second end of the second frame 122 is connected with the keycap 11. Moreover, the second frame 122 comprises a second keycap post 1221 and a second base post 1222. The second frame 122 is connected with the fixed keycap hook 112 of the keycap 11 through the second keycap post 1221. The second frame 122 is connected with the movable base hook 152 of the metallic base plate 15 through the second base post 1222.
The operations of the conventional key structure 1 in response to the depressing action of the user will be illustrated as follows. Please refer to FIGS. 1 and 2 again. When the keycap 11 is depressed, the keycap 11 is moved downwardly to push the scissors-type connecting element 12 in response to the depressing force. As the keycap 11 is moved downwardly relative to the metallic base plate 15, the keycap 11 pushes the corresponding rubbery elastomer 13. At the same time, the rubbery elastomer 13 is subjected to deformation and penetrated through the base opening 151 to push the membrane switch circuit member 14 and trigger the corresponding key intersection of the membrane switch circuit member 14. Consequently, the membrane switch circuit member 14 generates a corresponding key signal. When the keycap 11 is no longer depressed by the user, no external force is applied to the keycap 11 and the rubbery elastomer 13 is no longer pushed by the keycap 11. In response to the elasticity of the rubbery elastomer 13, the rubbery elastomer 13 is restored to its original shape to provide an upward elastic restoring force. Consequently, the keycap 11 is returned to its original position where it is not depressed.
The above key structure is used in a keyboard module of a notebook computer. In comparison with the keyboard of a desktop computer, the keyboard module of the notebook computer is thinner and the keycap of the keyboard module is slimmer. Consequently, the keyboard module of the notebook computer is favored by many users. However, the conventional key structure 1 still has some drawbacks. For example, there is a gap g between the first base post 1212 and the fixed base hook 153. Due to the gap g, the first base post 1212 and the fixed base hook 153 can be assembled with each other more easily. However, the gap g may easily cause a rocked condition of the first frame 121. Under this circumstance, the overall stability of the conventional key structure 1 is adversely affected. Moreover, while the conventional key structure 1 is operated, the gap g may cause collision between the first base post 1212 and the fixed base hook 153. Under this circumstance, unpleasant noise is generated.
Therefore, there is a need of providing a key structure with increased stability and low noise.